Minnesotans who haven’t seen their favorite lake since last fall might find that it has put on a few acres.

Heavy rains in recent weeks have swelled state lakes and rivers so much that swimmers and boaters — many beginning school summer vacations this weekend — are finding docks under water, boat launches flooded, beaches closed and wave-reducing speed restrictions on boats.

The high-water drama is especially noticeable on Lake Minnetonka, the metro area’s biggest and busiest recreational lake, where a floating bog that looks like an island had to be lassoed and anchored back into place Wednesday after it drifted away on high water and blocked a channel.

Although the sprawling lake’s water level dropped a fraction of an inch Wednesday from the record it had attained Tuesday, officials continued to warn of a continuing risk of floating obstacles — trees, parts of docks that have been pulled apart, pieces of firewood and other yard items the rising water has abducted. Boat launches are shorter than usual and boats themselves are tugging at taut moorings.

“Every day there’s been something floating in to shore,” said Gabriel Jabbour, who owns Tonka Bay Marina and other Lake Minnetonka boat services. He and other marina operators have cut power to many docks where electrical service lines are now running under water, and told boat owners to clear food out of refrigerators and perhaps loosen the mooring lines on boats that have risen nearly 5 inches in the past week alone.

The Minnesota Department of Natural Resources said caution is in order around the state, particularly with more thunderstorms expected Thursday through Saturday.

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High water in Lake Minnetonka meant docks were mostly submerged at the Deephaven City Marina on Wednesday.

“We are asking boaters, paddlers and swimmers not to let their guard down,” said Kara Owens, the DNR’s boat and water safety specialist. “Lake waters and rivers are high, and that water is moving fast. When the water is as high as it is, it moves a lot faster.”

A no-wake zone was re-established this week along the St. Croix River from Taylors Falls, Minn., to Prescott, Wis., and the U.S. Army Corps of Engineers closed the three Minneapolis locks on the Mississippi River to recreational boats for the third time this season. A no-wake restriction was also in place at Lake Minnetonka to reduce wave damage to shorelines.

In Edina, Minnehaha Creek continued to rise Wednesday, as water from Lake Minnetonka moved downstream. But flooding has not worsened and demand for sandbags has ebbed, officials said. Three homes and one church along the creek have been flooded.

Water won’t go down fast

Out on Lake Minnetonka, workers Wednesday lassoed the floating bog — a mass of cattails and roots about an acre in size — that had been blocking Seton Channel under County Road 15 between Spring Park and Mound, towed it back across a bay to where rising water had uprooted it and anchored it back into place with telephone poles.

Shawn Erdman, foreman for THN Enterprises, said the bog might reroot itself when the water levels on the lake drop. But that may take weeks.

“Water levels are going to remain high for some time,” Minnehaha Creek Watershed District spokeswoman Telly Mamayek said. “People need to understand there’s so much water out there, it’s going to take a while.”

At Grays Bay dam, where water from the lake flows into the head of Minnehaha Creek, flow has been at the legal maximum of 300 cubic feet per second for more than four weeks, which appears to be the longest stretch on record, Mamayek said.

But Wednesday, another 262 cubic feet per second was flowing over a weir next to the dam, where there was essentially no difference between the level of the lake and that of the creek.

Steve Olson of Minnetonka was walking his dog, Millie, at the Grays Bay dam looking for a place the dog might swim. He said he’d seen such conditions only once before in his 30 years living in the area.

“It’s kind of unique, going from drought to this,” Olson said.

Indeed, the U.S. Drought Monitor had indicated that the metro area was enduring a “moderate drought” from last summer through the snowy winter until the end of February.

Two Lake Minnetonka beaches — Crescent Beach in Shorewood and Nocomo Beach in Deephaven — remained closed Wednesday due to excessive contaminants in the water, and will remain so until daily testing finds the contaminants have been diluted to safe levels.

Three beaches in Mound, closed earlier in the week after a sewage release, were reopened Tuesday.

Lapping at roads, homes

In some areas along Lake Minnetonka, high water has closed small neighborhood roads and surrounded some homes.

DAVID JOLES &#x2022; djoles@startribune.com, Star Tribune

“Every day there’s been something floating in to shore,” said Gabriel Jabbour, a former Orono mayor and owner of Tonka Bay Marina in Excelsior Bay, where water was high Wednesday.

At Ace Hardware in Navarre, store manager Patti Briggs said she’d been selling a lot of sump pumps, squeegees and shop vacuum cleaners in recent days, many to customers wearing flood boots. Her supply of 18- and 24-inch zip ties was gone, she added; that seemed to be the length preferred by homeowners who wanted to reinforce connections between dock parts so they wouldn’t break away.

Jabbour, who has lived around the lake for several decades, said he thinks development — more pavement, bigger rooftops, filling of wetlands — has “changed the behavior of the lake,” causing it to rise faster and stay higher longer after rains.

But dealing with it this weekend, barring more heavy rain, should require only “some minor adjustments in life,” he said. “I’m just telling people to take it easy.”